R-trees, as in The R-tree: An Efficient and Robust Access Method for Points and Rectangles, Beckmann, Kriegel, Schneider and Seeger, Proc. ACM Int. Conf. on Management of Data, 1990

X-trees, as in The X-tree: An Index Structure for High-Dimensional Data, Berchtold, Keim and Kriegel, Proc. 22th Int. Conf. on Very Large Databases, 1996

Future work planned includes performance enhancements, incorporation of more index structures, and some work on supporting more optimal indexing when the entire set of data is known at index creation time; for more details, see the TODO file in the binary distribution.

The code is licensed BSD-style, and is intended to be similar in spirit to Nathan Froyd's TREES Library.